Add
chopped onions to pan and cook a couple minutes. Add chiles and garlic
and cook just a minute more. Add stock, tomatoes, corn, cumin and salt
to taste. Bring to a boil and then lower to a simmer. Cover and cook
for 15 minutes, then add chicken and cook till heated through.

Serve with avocado, cheese, cilantro, tortilla strips and a sprinkle of lime juice if desired.